How to identify Fuchsite with Ruby

To correctly identify Fuchsite with Ruby (Chromian Muscovite (Fuchsite) with Corundum (Ruby)), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Vibrant green (fuchsite) with contrasting red to pinkish-red (ruby) inclusions. The green can vary in intensity, and the ruby can be opaque to translucent.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Fuchsite: Pearly to vitreous. Ruby: Adamantine to vitreous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Schistose or foliated due to the micaceous nature of fuchsite, with harder, granular ruby crystals embedded within. Can feel somewhat greasy or soapy due to the mica.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Fuchsite: Platy, flaky, or massive aggregates. Ruby: Hexagonal prisms, tabular, or anhedral (irregular) grains.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Fuchsite: Perfect basal cleavage in one direction, producing thin, flexible sheets. Ruby: No cleavage, but exhibits parting along basal and rhombohedral planes.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Metamorphic terrains, particularly those derived from chromium-rich mafic or ultramafic protoliths, often associated with regional or contact metamorphism and metasomatic alteration.

Key Facts

Hardness

Fuchsite: 2.5-3 (Mohs). Ruby: 9 (Mohs). The overall rock hardness is variable.

Specific Gravity

Fuchsite: 2.77-2.88. Ruby: 3.97-4.05. The rock's specific gravity will be an average of its components.

Crystal System

Fuchsite: Monoclinic. Ruby: Hexagonal (Trigonal).

Color

Green (fuchsite) and Red (ruby).

Luster

Pearly (fuchsite) to Vitreous/Adamantine (ruby).

Transparency

Fuchsite: Translucent to opaque. Ruby: Opaque to translucent, rarely transparent.

Fracture

Fuchsite: Uneven to splintery. Ruby: Conchoidal to uneven.

Cleavage

Fuchsite: Perfect basal cleavage {001}. Ruby: No cleavage, but parting on {0001} and {1011}.

Composition

Fuchsite: K(Al,Cr)2(AlSi3O10)(OH)2 (Chromian Muscovite). Ruby: Al2O3 (Chromian Corundum).

Physical characteristics

• Crystal Habit: Fuchsite: Micaceous, platy, foliated. Ruby: Prismatic, tabular, granular, massive.
• Cleavage Type: Fuchsite: Perfect basal. Ruby: None (parting present).
• Fracture Type: Fuchsite: Uneven to splintery. Ruby: Conchoidal to uneven.
• Tenacity: Fuchsite: Flexible, elastic. Ruby: Brittle.
• Luster Type: Fuchsite: Pearly. Ruby: Vitreous to adamantine.

Explore Fuchsite with Ruby